KR20080011556A - Method of forming a contact - Google Patents

Abstract

A method for forming a contact is provided to easily control the polishing quantity of an interlayer dielectric by forming a multilayered structure as an interlayer dielectric wherein the multilayered structure includes first and second interlayer dielectrics with etch selectivity. A first interlayer dielectric(106) is formed on a substrate(100). A second interlayer dielectric is formed on the first interlayer dielectric, made of a material having etch selectivity with respect to a material constituting the first interlayer dielectric. The second and first interlayer dielectrics are patterned to form a contact hole partially exposing the substrate. The contact hole is filled with a conductive pattern. The second interlayer dielectric is removed to make the upper portion of the conductive pattern protrude from the first interlayer dielectric. The protruding conductive pattern is removed to form a contact(116). The process for forming the conductive pattern can include the following steps. A conductive layer is formed on the second interlayer dielectric to completely bury the contact hole. The conductive layer is planarized to expose the upper surface of the second interlayer dielectric.

Description

Method of forming a contact

1 to 8 are schematic process cross-sectional views illustrating a method for forming a contact according to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

100 semiconductor substrate 102 lower pattern

104: etch stop film 106: first interlayer insulating film

108: second interlayer insulating film 110: mask pattern

112: contact hole 114: conductive pattern

116: Contact

The present invention relates to a method of forming a contact. More specifically, it relates to a method of forming a contact having a high aspect ratio.

As the manufacturing techniques of semiconductor devices have been developed and their application to memory devices has been expanded, memory devices having high capacities have been developed. In particular, DRAM devices, in which memory cells are composed of one capacitor and one transistor, have been significantly improved in density.

As the degree of integration of a semiconductor device increases, the size of the contact connecting the device and the device or the layer and the layer with a conductive material decreases, while the thickness of the interlayer insulating film increases.

Here, in the process of forming a contact in the interlayer insulating film, first, a photoresist pattern is formed on the interlayer insulating film, and dry etching is performed using the photoresist pattern as an etching mask to form a contact hole in the interlayer insulating film. . At this time, the contact hole has a narrow line width from the upper to the lower by dry etching characteristics. Therefore, the thicker the interlayer insulating film, the greater the difference between the upper and lower line widths of the contact holes.

Subsequently, a conductive film is formed on the interlayer insulating film so as to fill the contact hole, and the upper surface of the conductive film is subjected to primary chemical mechanical polishing until the upper surface of the interlayer insulating film is exposed. During the first chemical mechanical polishing process, a dishing phenomenon occurs in a portion of the conductive film filling the contact hole, so that a portion of the upper part of the interlayer insulating film is removed to remove the conductive film having the dishing. The process must be carried out.

Subsequently, in order to reduce the line width difference between the upper and lower portions of the contact, the upper portion of the contact and the upper portion of the interlayer insulating layer may be removed by performing a tertiary chemical mechanical polishing process. In this case, the tertiary chemical mechanical polishing process is performed twice in the process of polishing the interlayer insulating film and the process for polishing the contact. Therefore, there is a problem that the process is very complicated and the process time and cost is high.

There is also a problem that it is difficult to precisely control the polishing amount of the interlayer insulating film to be polished.

SUMMARY OF THE INVENTION An object of the present invention for solving the above problems is to provide a method for forming a contact in which the difference in line width between the top and bottom is reduced, the process is simple, and the amount of polishing of the interlayer insulating film is easily controlled.

According to an aspect of the present invention for achieving the above object, in the contact forming method, to form a first interlayer insulating film on a substrate. A second interlayer insulating layer formed of a material having an etch selectivity with respect to a material forming the first interlayer insulating layer is formed on the first interlayer insulating layer. Patterning the second interlayer insulating film and the first interlayer insulating film to form a contact hole for partially exposing the substrate. A conductive pattern filling the contact hole is formed. The second interlayer insulating layer is removed to protrude an upper portion of the conductive pattern from the first interlayer insulating layer. The protruding conductive pattern portion is removed to form a contact.

The first interlayer insulating layer may be formed of an oxide, and the second interlayer insulating layer may be formed of nitride. The oxides include BPSG (Boro-Phospho Silcate Glass), USG (Undoped Silicate Glass), PSG (Phosphorus doped Silicate Glass), BSG (Boron doped Silicate Glass), PETEOS (Plasma Enhanced Tetra Ethyl Ortho Silicate) or HDP (High Density) Plasma) oxide can be used. The second interlayer insulating layer may be etched by wet etching. The conductive pattern may be formed by forming a conductive film on the second interlayer insulating film so as to completely fill the contact hole, and planarizing the conductive film so that an upper surface of the second interlayer insulating film is exposed.

According to the present invention as described above, by removing a portion of the upper portion of the contact can reduce the line width difference between the upper and lower, the interlayer insulating film is made of two materials having an etch selectivity, it is easier to remove the polishing amount of the interlayer insulating film The process steps can also be simplified compared to conventional methods.

Hereinafter, a method for forming a contact according to an embodiment of the present invention will be described in detail.

1 to 8 are cross-sectional views illustrating a method of forming a contact according to an embodiment of the present invention.

Referring to FIG. 1, an etch stop layer 104 is formed on a semiconductor substrate 100.

The etch stop layer 104 may then function as a film for confirming the end point of the etching process while the interlayer insulating layer is formed and then the interlayer insulating layer is etched. The etch stop layer 104 may include nitride, and examples thereof include silicon nitride.

The lower pattern 102 may be formed under the etch stop layer 104, and the lower pattern 102 may be electrically connected to the upper pattern by a contact 116 formed after the conductive material. .

Referring to FIG. 2, a first interlayer insulating layer 106 is formed on the etch stop layer 104.

The first interlayer insulating layer 106 includes an oxide, and examples of the oxide include Boro-Phospho Silcate Glass (BPSG), Undoped Silicate Glass (USG), Phosphorus doped Silicate Glass (PSG), and Boron doped Silicate Glass (BSG). , PETEOS (Plasma Enhanced Tetra Ethyl Ortho Silicate) or HDP (High Density Plasma) oxide. Here, since the first interlayer insulating film 106 contains an oxide, the first interlayer insulating film 106 is etched in the HF diluent.

In this case, the height of the first interlayer insulating layer 106 is formed to be the same as the height of the desired contact 116. This will be described later in detail.

Referring to FIG. 3, a second interlayer insulating layer 108 made of a material having an etch selectivity with respect to a material forming the first interlayer insulating layer 106 is formed on the first interlayer insulating layer 106.

In this case, since the second interlayer insulating layer 108 should have an etching selectivity with respect to the same etching solution as the first interlayer insulating layer 106 may include nitride. Silicon nitride etc. are mentioned as an example of the said nitride. Wherein the silicon nitride has the property of being etched by H ₃ PO ₄ solution.

That is, when the HF diluent is used as an etching solution, the first interlayer insulating film 106 is etched faster than the second interlayer insulating film 108, whereas when the H ₃ PO ₄ solution is used as the etching solution, the first interlayer insulating film 106 is etched. Etching is slower than the second interlayer insulating film 108.

Referring to FIG. 4, a mask pattern 110 is formed on the second interlayer insulating layer 108 to partially expose the second interlayer insulating layer 108.

In this case, the mask pattern 110 may be a photoresist pattern, and a portion exposed by the mask pattern 110 may be a portion where the contact 116 will be formed later. Therefore, a lower pattern 102 in contact with the contact 116 is positioned below the exposed portion.

Referring to FIG. 5, the second interlayer insulating layer 108 and the first interlayer insulating layer 106 are sequentially etched using the mask pattern 110 as an etch mask to expose the etch stop layer 104. A preliminary contact hole (not shown) is formed.

In this case, the etching process is a dry etching, the preliminary contact hole formed by the dry etching has a shape in which the line width becomes narrower from the top to the bottom.

Subsequently, the etch stop layer 104 exposed on the bottom surface of the preliminary contact hole is removed to form a contact hole 112 exposing the lower pattern 102 formed under the etch stop layer 104.

Although not shown, after forming the contact hole 112, the mask pattern 110 is removed. When the mask pattern 110 is a photoresist pattern, the photoresist pattern may be removed by an ashing and strip process.

Referring to FIG. 6, a conductive film (not shown) is formed on the second interlayer insulating layer 108 to fill the contact hole 112.

Subsequently, a conductive pattern 114 is formed by performing a first chemical mechanical polishing process on a portion of the upper surface of the conductive layer so that the upper surface of the second interlayer insulating layer 108 is exposed. During the first chemical mechanical polishing process, dishing may occur in which the upper center of the conductive pattern 114 is partially lost.

In this case, the conductive pattern 114 is higher than the height of the desired contact 116 by the thickness of the second interlayer insulating layer 108.

Referring to FIG. 7, the second interlayer insulating layer 108 is removed to protrude an upper portion of the conductive pattern 114 from the first interlayer insulating layer 106.

The second interlayer insulating layer 108 is removed by wet etching, and since the second interlayer insulating layer 108 includes nitride, an H ₃ PO ₄ solution is used as the etching solution.

In this case, while the wet etching process is performed, the first interlayer insulating film (oxide) 106 and the conductive pattern (conductive material) 114 are hardly etched because they are made of a material having an etching selectivity with nitride.

Accordingly, the upper surface of the first interlayer insulating layer 106 is exposed by the wet etching process, and the upper surface and a portion of the upper side surface of the conductive pattern 114 are exposed. That is, part of the conductive pattern 114 protrudes from the surface of the first interlayer insulating layer 106.

Referring to FIG. 8, the protruding conductive pattern 114 is removed by performing a second chemical mechanical polishing process to form a contact 116 having the same height as the surface of the first interlayer insulating layer 106.

As illustrated in FIG. 2, the first interlayer insulating layer 106 is formed at the same height as the desired contact 116, thereby removing an upper portion of the conductive pattern 114 protruding from the surface of the first interlayer insulating layer 106. A contact 116 having the same height as that of the first interlayer insulating layer 106 may be formed.

As described above, the interlayer insulating film is formed into a multi-layer structure including a first interlayer insulating film 106 and a second interlayer insulating film 108 having an etching selectivity, thereby selectively removing the second interlayer insulating film 108 by wet etching. It may be easy to adjust the amount of polishing the interlayer insulating film that occurred in the. In addition, after removing the second interlayer insulating layer 108, the upper line width may be reduced by removing the upper portion of the protruding conductive pattern 114, thereby reducing the line width difference from the lower portion.

In addition, the number of chemical mechanical polishing processes may be reduced, thereby simplifying the process and reducing the cost and time required.

As described above, according to the preferred embodiment of the present invention, the process steps can be further simplified, thereby reducing the cost and processing time.

In addition, by forming the interlayer insulating film in a multilayer structure of the first interlayer insulating film and the second interlayer insulating film having an etching selectivity, it is possible to easily control the amount of polishing of the interlayer insulating film.

In addition, the line width of the upper portion is reduced to prevent bridges or short circuits between adjacent contacts in advance.

While the foregoing has been described with reference to preferred embodiments of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

Claims (5)

Forming a first interlayer insulating film on the substrate; Forming a second interlayer insulating film made of a material having an etch selectivity with respect to a material forming the first interlayer insulating film on the first interlayer insulating film; Patterning the second interlayer insulating film and the first interlayer insulating film to form a contact hole partially exposing the substrate; Forming a conductive pattern to fill the contact hole; Removing the second insulating interlayer to protrude an upper portion of the conductive pattern from the first insulating interlayer; And And forming a contact by removing the protruding conductive pattern portion. The method of claim 1, wherein the first interlayer insulating layer is formed of an oxide, and the second interlayer insulating layer is formed of a nitride. The method of claim 2, wherein the oxide comprises: Boro-Phospho Silcate Glass (BPSG), Undoped Silicate Glass (USG), Phosphorus doped Silicate Glass (PSG), Boron doped Silicate Glass (BSG), Plasma Enhanced Tetra Ethyl Ortho Silicate (PETOS) Or HDP (High Density Plasma) oxide. The method of claim 2, wherein the second interlayer insulating layer is etched by wet etching. The method of claim 1, wherein the method of forming the conductive pattern is performed. Forming a conductive film on the second interlayer insulating film to completely fill the contact hole; And And planarizing the conductive film to expose an upper surface of the second interlayer insulating film.

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